Two of the three enzymes responsible for the catabolism of xylitol by Lactobacillus casei, namely the transport component Enzyme IIIxt1 and xylitol-5-phosphate dehydrogenase, have been purified to electrophoretic homogeneity and are presently being characterized. Both enzymes are unusual in that they contain significant amounts of lipid. Antisera have been prepared against the two enzymes and are being used as probes to (1) detect and measure structural homology between isofunctional counterparts in other bacteria and (2) to completely characterize the genetic lesions in our large catalogue of mutants. Adherence studies with gram negative oral bacteria have been extended to include strains of Actinobacillus actinomycetemcomitans. Like the oral Cytophaga strains described in our earlier studies, actinobacilli are capable of adsorbing to spheroidal hydroxyapatite (SHA) in comparatively high numbers. Serum and saliva treatment of the SHA inhibited adsorption. Treatment of the cells with various proteases, phospholipases and neuraminidase provided a means of distinguishing between strains based on binding capabilities.